sent-mas Physics l Q3. A string, tied to a sinusoidal oscillator at P and running over a support at Q, is stretched by a , block of mass m, as shown in Figure 3. The separation i. between P and Q is 1.2 m, and the- frequency f of the oscillator is fixed at 50 Hz. The amplitude of the motion at P is small enough for that point to be cansidered a node. A node also exists at Q. A standing wave appears when the mass of the hanging block is 100 g or 225 g, but not for any mass in between. Calculate the linear density n of the string in g/m. (10 marks) Oscillator (Remarks: The gure given is for reference only. The harmonic number may not be 4.) Figure 3